Osteoid osteomas are benign, but painful, tumors that mainly occur in children and young adolescents, accounting for 10-12 percent of benign bone tumors with 80 percent of patients being between 5-24 years of age. Most osteoid osteomas are elongated in shape, have little or no growth potential, and rarely exceed 1.5 centimeters in diameter. There are typically three approaches to treatment: (1) medical treatment, which includes the administration of aspirin or other nonsteroidal anti-inflammatory agents that can be used in the long term; (2) surgical treatment, which involves resecting the tumor from the bone; and (3) radio frequency (RF) treatment, which involves percutaneously inserting an ablation needle within the bone and ablating the tumor with RF energy.
With regard to medical treatment, the pain is often intolerable and long-term use of nonsteroidal anti-inflammatory agents can result in gastrointestinal side effects. Surgery can be challenging due to difficulties in identification, incomplete removal of the tumor, and the adverse effect of the resection on a weight-bearing bone. RF ablation has become the method preferred by most doctors, because of its percutaneous, less invasive advantages. This technology allows the tumor to be ablated (burnt) by an electrode that is placed in the center of the nidus of the tumor.
Currently, percutaneous RF ablation can be accomplished using a multiple needle electrode probe or a single needle electrode probe. Multiple needle electrode probes are intended for soft tissue tumors and are somewhat limited in bone tumor applications, mainly due to the relatively small size of osteoid osteomas and the difficulty of penetrating the hard bone tissue with the relatively flexible electrodes. Although the size and hard tissue penetration considerations of single needle electrode probes are more ideal, the greatest challenge when using single-needle probes is to create the largest ablation area to coincide with the elongated geometry of the tumor. However, because single needle electrodes tend to favor a spherical ablation, the elongated osteoid osteomas must be treated with multiple ablations, requiring the electrode to be repositioned for subsequent ablations in order to prevent or minimize the destruction of healthy tissue.
There, thus, remain a need to provide tissue ablation probes and tissue ablation methods for treating tumors within bone tissue, such as osteoid osteomas.